The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
According to a continuous demand for improvement of fuel efficiency for a vehicle and stricter regulations of discharge gas of countries, a demand for an environmentally-friendly vehicle has been increased, and a hybrid vehicle has been provided as a realistic alternative for the demand.
The hybrid electric vehicle is a vehicle using two or more power sources. Two or more power sources may be combined by various schemes. Here, as the power source, a combination of a gasoline engine (or a diesel engine) using traditional fossil fuel and a motor/generator driven by electrical energy is used. The hybrid vehicle may provide appropriate output torque depending on how the two power sources (i.e., the engine and the motor) are harmoniously operated.
The hybrid vehicle provides an electric vehicle (EV) mode in which the vehicle runs by a torque of only the motor, a hybrid electric vehicle (HEV) mode in which the vehicle runs by the sum of an engine torque and a motor torque according to whether the engine clutch couples, and a regenerative braking (RB) mode which recovers braking and inertial energy generated when braking applies to the vehicle or when the vehicle is driven by inertia energy of the vehicle. In the RB mode, the braking and inertial energy runs the driving motor and power is generated such that the recovered braking and inertial energy charges a battery.
A regenerative braking system uses a portion of a braking force for power generation upon braking a vehicle, charges generated electrical energy in a battery, and uses a portion of kinetic energy from a driving speed of a vehicle as energy desired for driving a generator (i.e., drive motor/generator). By extending a travel distance of a vehicle by such a regenerative braking system, fuel efficiency can be improved and discharge of a noxious gas can be reduced.
When the regenerative braking is controlled in collaboration with the hydraulic pressure braking, the hydraulic pressure braking is primarily performed in order to obtain braking stability and initial braking hydraulic pressure. According to the conventional art, since it is very difficult to predict a regenerative braking amount and a reliability of the regenerative braking amount is very low, a hydraulic pressure braking is primarily performed.
There is a limitation for retrieving energy through the regenerative braking when the hydraulic pressure braking is primarily performed, fuel consumption is deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.